Volatile components from European liverworts Marsupella emarginata,M. aquatica and M. alpina

The hydrodistillation products of the liverworts Marsupella emarginata, M. aquatica and M. alpina were investigated by spectroscopic methods. A number of new compounds could be isolated by preparative gas chromatography (GC) and identified by spectroscopic techniques including GC-mass spectrometry, NMR and chemical correlations in conjunction with enantioselective GC. From M. emarginata, in addition to many known compounds, the sesquiterpene hydrocarbon (-)-7-epi-eremophila-1(10),8,11-triene (1) and the sesquiterpene derivatives (-)-4-epi-marsupellol (2), (-)-marsupellol acetate (18), (-)-4-epi-marsupellol acetate (4), (+)-5-hydroxymarsupellol acetate (5) and (-)-9-acetoxygymnomitr-8(12)-ene (24) could be identified. In M. aquatica the sesquiterpene hydrocarbons (-)-myltayl-8(12)-ene (7), ent-(+)-amorpha-4,11-diene (8), (-)-amorpha-4,7(11)-diene (9), the sesquiterpene alcohol (+)-9-hydroxyselina-4,11-diene (10) and (-)-2-acetoxyamorpha-4,7(11)-diene (11) were identified. In M. alpina (-)-trans-selina-4(15),11-dien-5-ol (12), (+)-8,9-epoxyselina-4,11-diene (13) and (+)-cis-selina-4(15),11-dien-5-ol (14) were found as new natural products.     

Cloning, expression, purification and characterization of recombinant (+)-germacrene D synthase from Zingiber officinale

A cDNA clone encoding a sesquiterpene synthase, (+)-germacrene D synthase, has been isolated from ginger (Zingiber officinale). The full-length cDNA (AY860846) contains a 1650-bp open reading frame coding for 550 amino acids (63.8kDa) with a theoretical pI=5.59. The deduced amino acid sequence is 30-46% identical with sequences of other sesquiterpene synthases from angiosperms. The recombinant enzyme, produced in Escherichia coli, catalyzed the formation of a major product, (+)-germacrene D (50.2% of total sesquiterpenoids produced) and a co-product, germacrene B (17.1%) and a number of minor by-products. The optimal pH for the recombinant enzyme is around 7.5. Substantial (+)-germacrene D synthase activity is observed in the presence of Mg2+, Mn2+, Ni2+ or Co2+, while the enzyme is inactive when Cu2+ or Zn2+ is used. The Km- and kcat-values are 0.88 microM and 3.34 x 10(-3) s(-1), respectively. A reaction mechanism involving a double 1,2-hydride shift has been established using deuterium labeled substrates in combination with GC-MS analysis.     

Absolute configuration of the alpha-methylbutyryl residue in longipinene derivatives from Stevia pilosa

The absolute configuration of the alpha-methylbutyryl residue in (4R,5S,7S,8S,9S,10R,11R,2'S)-7-angeloyloxy-9-hydroxy-8-(alpha-methylbutyryloxy)-longipin-2-en-L-one and (4R,5S,7S,8R,10R,11R,2'S)-7-angeloyloxy-8-(alpha-methylbutyryloxy)- longipin-2-en-L-one was determined by chemical correlation with (S)-(+)-benzyl alpha-methylbutyrate prepared from authentic (S)-(+)-alpha-methylbutyric acid. Both compounds were isolated from the hexane extracts of roots of Stevia pilosa Lag. together with four other longipinene derivatives. The developed correlation method is useful to ascertain the chirality of natural alpha-methylbutyryl esters found in nature and to reinforce the hypotheses on the biogenetic origin of these residues.     

Synthesis of (+)-(2R,3S,4R)-2,3,4-trihydroxycyclohexanone from D-glucose

We have described the synthesis of (+)-(2R,3S,4R)-2,3,4-trihydroxycyclohexanone by the reduction of a keto-conduritol derivative, the latter being prepared in five steps from (-)-(2S,3R,4S,5S)-2,3,4-tribenzyloxy-5-hydroxycyclohexanone, which is in turn readily synthesized from D-glucose.     

Sesquiterpene constituents from the liverwort Bazzania japonica

The hydrodistillation products of the liverwort Bazzania japonica were separated by preparative gas chromatography (GC) and investigated by spectroscopic methods. Seven unknown compounds were isolated and identified by GC-MS and NMR. Four of them, the norsesquiterpene hydrocarbons 4-epi-11-nor-aristola-1(10),11-diene (1), 4-epi-11-nor-aristola-1,9,11-triene (2), 4-epi-11-nor-aristola-9,11-diene (3), and one oxygenated sesquiterpene, (-)-aristol-1(10)-en-12-ol (5) are new natural compounds, and one, (+)-himachala-2,4-diene (7), has for the first time been isolated from liverworts. The absolute configurations of 5 and 7 were derived by chemical correlation reactions and/or enantioselective GC using cyclodextrin phases. 1, 2 and 3 have identical absolute configuration.     

Quinolizidine alkaloids from the curare adjuvant Clathrotropis glaucophylla

The bark of Clathrotropis glaucophylla (Fabaceae) is used as admixture of curare arrow poison by the Yanomami; Amerindians in Venezuela. A new quinolizidine alkaloid (QA), (-)-13alpha-hydroxy-15alpha-(1-hydroxyethyl)-anagyrine [(-)-clathrotropine], was isolated from the alkaloid extract of C. glaucophylla bark, together with eleven known QAs: (-)-anagyrine, (-)-thermopsine, (-)-baptifoline, (-)-epibaptifoline, (-)-rhombifoline, (-)-tinctorine, (-)-cytisine, (-)-N-methylcytisine, (-)-lupanine, (-)-6alpha-hydroxylupanine and (+)-5,6-dehydrolupanine. The isolation and structure elucidation were performed with the aid of chromatographic (TLC, HPLC and CC) and spectroscopic (UV and 1D/2D NMR) methods, and mass spectrometry. To our knowledge, this is the first time quinolizidine alkaloids have been isolated from an arrow poison ingredient. It is also the first report on Clathrotropis species being used for preparation of arrow poison.     

Biosynthesis of germacrene A carboxylic acid in chicory roots. Demonstration of a cytochrome P450 (+)-germacrene a hydroxylase and NADP+-dependent sesquiterpenoid dehydrogenase(s) involved in sesquiterpene lactone biosynthesis

Sprouts of chicory (Cichorium intybus), a vegetable grown in the dark, have a slightly bitter taste associated with the presence of guaianolides, eudesmanolides, and germacranolides. The committed step in the biosynthesis of these compounds is catalyzed by a (+)-germacrene A synthase. Formation of the lactone ring is the postulated next step in biosynthesis of the germacrene-derived sesquiterpene lactones. The present study confirms this hypothesis by isolation of enzyme activities from chicory roots that introduce a carboxylic acid function in the germacrene A isopropenyl side chain, which is necessary for lactone ring formation. (+)-germacrene A is hydroxylated to germacra-1(10),4,11(13)-trien-12-ol by a cytochrome P450 enzyme, and is subsequently oxidized to germacra-1(10),4,11(13)-trien-12-oic acid by NADP+-dependent dehydrogenase(s). Both oxidized germacrenes were detected as their Cope-rearrangement products elema-1,3,11(13)-trien-12-ol and elema-1,3,11(13)-trien-12-oic acid, respectively. The cyclization products of germacra-1(10),4,11(13)-trien-12-ol, i.e. costol, were also observed. The (+)-germacrene A hydroxylase is inhibited by carbon monoxide (blue-light reversible), has an optimum pH at 8.0, and hydroxylates beta-elemene with a modest degree of enantioselectivity.     

(-)-Amarbellisine, a lycorine-type alkaloid from Amaryllis belladonna L. growing in Egypt

A new lycorine-type alkaloid, named (-)-amarbellisine, was isolated from the bulbs of Egyptian Amaryllis belladonna L. together with the well known alkaloids (-)-lycorine, (-)-pancracine, (+)-vittatine, (+)-11-hydroxyvittatine, and (+)-hippeastrine. The new alkaloid, containing the pyrrolo[de]phenanthridine ring system, was essentially characterised by spectroscopic and optical methods, and proved to be the 2-methoxy-3a,4,5,7,11b,11c-hexahydro-1H-[1,3]dioxolo[4,5-j]pyrrolo[3,2,1-de]phenanthridinol. By using HPTLC technique we also carried out a comparative study of the relative and total alkaloidal content at two different stages of plant growth. Finally, the antimicrobial activity of the isolated alkaloids was assayed.     

Chemosystematic investigations of irregular diterpenes in Anisotome and related New Zealand Apiaceae

A chemosystematic HPLC-UV and HPLC-MS investigation of New Zealand members of the Apiaceae was performed. Diterpenes were identified and quantified in methanolic extracts from subaerial parts of 28 taxa and 54 samples of Aciphylla, Anisotome, Apium, Gingidia, Lignocarpa, Oreomyrrhis, and Scandia. Six diterpenes (1-2, 4-7) and four polyacetylenes (8-11) were identified. The known compounds were the diterpenes anisotomenoic acid 1, anisotomene-1-ol 2, 16-acetoxyanisotomenoic acid 4 and anisotomene-1,12-diol 5; and the polyacetylenes falcarinol 8, falcarindiol 9, (+)-9(Z),17-octadecadiene-12,14-diyne-1,11,16-triol 10, and (+)-9(Z),17-octadecadiene-12,14-diyne-1,11,16-triol 1-acetate 11. New irregular diterpenes 13,14-dihydroanisotom-12E-ene-1,14-diol 6 and 14-methoxy-13,14-dihydroanisotom-12E-ene-1-ol 7 were isolated from A. haastii. Isomers of the new semi-synthetic diterpene 16-hydroxyanisotomenoic acid 3 were detected in extracts of Anisitone flexuosa. Structure elucidation was performed by HR mass spectrometry and 1D and 2D NMR spectroscopy. In crude extracts, compounds were identified by their HPLC retention times and their on-line HPLC-UV and MS spectra. Anisotomene diterpenes occurred in eight out of 16 species of the genus Anisotome, but were not detected in any of the other genera. In contrast, polyacetylenes were present in all the genera investigated.     

(+)-(10R)-Germacrene A synthase from goldenrod,Solidago canadensis; cDNA isolation,bacterial expression and functional analysis

Profiling of sesquiterpene hydrocarbons in extracts of goldenrod, Solidago canadensis, by GC-MS revealed the presence of both enantiomers of germacrene D and lesser amounts of germacrene A, alpha-humulene, and beta-caryophyllene. A similarity-based cloning strategy using degenerate oligonucleotide primers, based on conserved amino acid sequences in known plant sesquiterpene synthases and RT-PCR, resulted in the isolation of a full length sesquiterpene synthase cDNA. Functional expression of the cDNA in E. coli, as an N-terminal thioredoxin fusion protein using the pET32b vector yielded an enzyme that was readily purified by nickel-chelate affinity chromatography. Chiral GC-MS analysis of products from of (3)H- and (2)H-labelled farnesyl diphosphate identified the enzyme as (+)-(10R)-germacrene A synthase. Sequence analysis and molecular modelling was used to compare this enzyme with the mechanistically related epi-aristolochene synthase from tobacco.     

Catalytic specificity of pea O-methyltransferases suggests gene duplication for (+)-pisatin biosynthesis

S-adenosyl-l-methionine: 2-hydroxyisoflavanone 4'-O-methyltransferase (HI4'OMT) methylates 2,7, 4'-trihydroxyisoflavanone to produce formononetin, an essential intermediate in the synthesis of isoflavonoids with methoxy or methylenedioxy groups at carbon 4' (isoflavone numbering). HI4'OMT is highly similar (83% amino acid identity) to (+)-6a-hydroxymaackiain 3-O-methyltransferase (HMM), which catalyzes the last step of (+)-pisatin biosynthesis in pea. Pea contains two linked copies of HMM with 96% amino acid identity. In this report, the catalytic activities of the licorice HI4'OMT protein and of extracts of Escherichia coli containing the pea HMM1 or HMM2 protein are compared on 2,7,4'-trihydroxyisoflavanone and enantiomers of 6a-hydroxymaackiain. All these enzymes produced radiolabelled 2,7-dihydroxy-4'-methoxyisoflavanone or (+)-pisatin from 2,7,4'-trihydroxyisoflavanone or (+)-6a-hydroxymaakiain when incubated with [methyl-(14)C]-S-adenosyl-l-methionine. No product was detected when (-)-6a-hydroxymaackiain was used as the substrate. HI4'OMT and HMM1 showed efficiencies (relative V(max)/K(m)) for the methylation of 2,7,4'-trihydroxyisoflavanone 20 and 4 times higher than for the methylation of (+)-6a-hydroxymaackiain, respectively. In contrast, HMM2 had a higher V(max) and lower K(m) on (+)-6a-hydroxymaackiain, and had a 67-fold higher efficiency for the methylation of (+)-6a-hydroxymaackiain than that for 2,7,4'-trihydroxyisoflavanone. Among the 15 sites at which HMM1 and HMM2 have different amino acid residues, 11 of the residues in HMM1 are the same as found in HI4'OMTs from three plant species. Modeling of the HMM proteins identified three or four putative active site residues responsible for their different substrate preferences. It is proposed that HMM1 is the pea HI4'OMT and that HMM2 evolved by the duplication of a gene encoding a general biosynthetic enzyme (HI4'OMT).     

Stereoselective reduction of ketones by various vegetables

Reduction of (+)-and (−)-camphorquinones (1a, 1b) by various vegetables (carrot, potato, sweet potato, apple, Japanese radish, cucumber, burdock and onion) gave -hydroxycamphor selectively. Using burdock, (+)-camphorquinone was reduced to give (−)-3S-exo-hydroxycamphor (4a) as major product in high stereoselectivity with high yield. Moreover, 1,2-cyclohexanedione (1c) and 2-methylcyclohexanone (1d) with various vegetables afford enantiomerically pure trans- and/or cis-alcohol, respectively. Various vegetable reduction gave a new idea of a biotechnological process.     

Differential nucleotide excision repair susceptibility of bulky DNA adducts in different sequence contexts: hierarchies of recognition signals

The structural origin underlying differential nucleotide excision repair (NER) susceptibilities of bulky DNA lesions remains a challenging problem. We investigated the 10S (+)-trans-anti-[BP]-N(2)-2'-deoxyguanosine (G*) adduct in double-stranded DNA. This adduct arises from the reaction, in vitro and in vivo, of a major genotoxic metabolite of benzo[a]pyrene (BP), (+)-(7R,8S,9S,10R)-7,8-dihydroxy-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene, with the exocyclic amino group of guanine. Removal of this lesion by the NER apparatus in cell-free extracts has been found to depend on the base sequence context in which the lesion is embedded, providing an excellent opportunity for elucidating the properties of the damaged DNA duplexes that favor NER. While the BP ring system is in the B-DNA minor groove, 5' directed along the modified strand, there are orientational distinctions that are sequence dependent and are governed by flanking amino groups [Nucleic Acids Res.35 (2007), 1555-1568]. To elucidate sequence-governed NER susceptibility, we conducted molecular dynamics simulations for the 5'-...CG*GC..., 5'-...CGG*C..., and 5'-...TCG*CT... adduct-containing duplexes. We also investigated the 5'-...CG*IC... and 5'-...CIG*C... sequences, which contain "I" (2'-deoxyinosine), with hydrogen replacing the amino group in 2'-deoxyguanosine, to further characterize the structural and dynamic roles of the flanking amino groups in the damaged duplexes. Our results pinpoint explicit roles for the amino groups in tandem GG sequences on the efficiency of NER and suggest a hierarchy of destabilizing structural features that differentially facilitate NER of the BP lesion in the sequence contexts investigated. Furthermore, combinations of several locally destabilizing features in the hierarchy, consistent with a multipartite model, may provide a relatively strong recognition signal.     

Volatile constituents in the liverwort Tritomaria polita

The essential oil of the liverwort Tritomaria polita, collected in Otztal/Tyrol (Austria), was investigated by chromatographic and spectroscopic methods. Several new compounds were isolated by preparative gas chromatography (GC) and their structures investigated by mass spectrometry (MS) and NMR techniques. In addition to known constituents, the sesquiterpenoids (+)-eudesma-3,11-dien-8-one, (+)-eudesma-3,7(11)-dien-8-one, (+)-6,11-epoxy-eudesmane, (-)-6,7-seco-eudesm-7(11)-en-6-al, (+)-6beta-hydroxy-eudesm-11-ene, (-)-6alpha-hydroxy-eudesm-11-ene, (+)-6,11-epoxy-isodaucane could be identified as natural compounds for the first time.     

Monoterpene double-bond reductases of the (-)-menthol biosynthetic pathway: isolation and characterization of cDNAs encoding (-)-isopiperitenone reductase and (+)-pulegone reductase of peppermint

Random sequencing of a peppermint essential oil gland secretory cell cDNA library revealed a large number of clones that specified redox-type enzymes. Full-length acquisitions of each type were screened by functional expression in Escherichia coli using a newly developed in situ assay. cDNA clones encoding the monoterpene double-bond reductases (-)-isopiperitenone reductase and (+)-pulegone reductase were isolated, representing two central steps in the biosynthesis of (-)-menthol, the principal component of peppermint essential oil, and the first reductase genes of terpenoid metabolism to be described. The (-)-isopiperitenone reductase cDNA has an open reading frame of 942 nucleotides that encodes a 314 residue protein with a calculated molecular weight of 34,409. The recombinant reductase has an optimum pH of 5.5, and K(m) values of 1.0 and 2.2 microM for (-)-isopiperitenone and NADPH, respectively, with k(cat) of 1.3s(-1) for the formation of the product (+)-cis-isopulegone. The (+)-pulegone reductase cDNA has an open reading frame of 1026 nucleotides and encodes a 342 residue protein with a calculated molecular weight of 37,914. This recombinant reductase catalyzes the reduction of the 4(8)-double bond of (+)-pulegone to produce both (-)-menthone and (+)-isomenthone in a 55:45 ratio, has an optimum pH of 5.0, and K(m) values of 2.3 and 6.9 microM for (+)-pulegone and NADPH, respectively, with k(cat) of 1.8s(-1). Deduced sequence comparison revealed that these two highly substrate specific double-bond reductases show less than 12% identity. (-)-Isopiperitenone reductase is a member of the short-chain dehydrogenase/reductase superfamily and (+)-pulegone reductase is a member of the medium-chain dehydrogenase/reductase superfamily, implying very different evolutionary origins in spite of the similarity in substrates utilized and reactions catalyzed.     

Terpenes from Otostegia integrifolia

The essential oil and chloroform extract of air-dried leaves of Otostegia integrifolia Benth. were investigated for the first time using analytical and preparative gas chromatography (GC), GC-mass spectrometry (MS) and NMR techniques. A total of 40 constituents including monoterpenes, sesquiterpenes, diterpenes and their derivatives were identified. A prenylbisabolane type diterpene, 1-methyl-4-(5,9-dimethyl-1-methylene-deca-4,8-dienyl)cyclohexene was identified as a major component. The chloroform extract of the leaves yielded two labdane type diterpenoids, 15,16-epoxy-3alpha,9alpha-dihydroxy-labda-13(16),14-diene and 9(13),15(16)-diepoxy-3alpha-hydroxy-16-dihydrolabda-14-ene, a saturated hydrocarbon, pentatriacontane, and stigmasterol. The structures of the isolated compounds were established by spectroscopic methods.     

Secondary metabolites from Ganoderma lucidum and Spongiporus leucomallellus

The hydrodistillates and solvent extracts of the fruit bodies of Ganoderma lucidum (Fr.) P. Karst. and Spongiporus leucomallellus (Murril) A. David were investigated. The constituents in both oils comprised hydrocarbons, monoterpenes, sesquiterpenes, and fatty acids. Major volatiles of G. lucidum were trans-anethol, R-(-)-linalool, S-(+)-carvone and alpha-bisabolol, while the essential oil of S. leucomallellus contained relatively large amounts of R-(-)-1-octene-3-ol, R-(-)-linalool, 1-hepten-3-one and (Z)-nerolidol. From the n-hexane extract of G. lucidum, the steroid ester ergosta-7,22-diene-3beta-yl pentadecanoate could be identified. From S. leucomallellus two constituents showing structures of 3,4-seco-lanostane type triterpene acids were identified as (+)-23-oxo-3,4-seco-lanosta-4(28),7(8),9(11),24(31)-tetraene-3,26-dicarboxylic acid and (+)-20-hydroxy-23-oxo-3,4-seco-lanosta-4(28),7(8),9(11),24(31)-tetraene3,26-dicarboxylic acid, respectively. Cytotoxicity and antimicrobial activity of selected compounds were investigated using standard tests.     

Antioxidant aryl-prenylcoumarin, flavan-3-ols and flavonoids from Eysenhardtia subcoriacea

Antioxidant activity (AOA) assay-guided chemical analysis, using a rat pancreas homogenate model, of aerial parts from Eysenhardtia subcoriacea, led to isolation of the new compound subcoriacin (3-(2'-hydroxy-4',5'-methylendioxyphenyl)-6-(3'-hydroxymethyl-4'-hydroxybut-2'-enyl)-7-hydroxycoumarin) together with the known substances: (+)-catechin, (-)-epicatechin, (+)-afzelechin, eriodictyol, (+)-catechin 3-O-beta-D-galactopyranoside and quercetin 3-O-beta-D-galactopyranoside as bioactive constituents. The structure of the compound was determined from 1D and 2D NMR spectroscopic analyses. Additional known constituents were characterized. The bioactive compounds showed also moderate to strong radical scavenging properties against diphenylpicrylhydrazyl radical (DPPH). In addition, subcoriacin, (+)-catechin, (-)-epicatechin and (+)-afzelechin improved the reduced glutathione levels in rat pancreatic homogenate.     

Fabacyl acetate, a germination stimulant for root parasitic plants from Pisum sativum

A germination stimulant, fabacyl acetate, was purified from root exudates of pea (Pisum sativum L.) and its structure was determined as ent-2′-epi-4a,8a-epoxyorobanchyl acetate [(3aR,4R,4aR,8bS,E)-4a,8a-epoxy-8,8-dimethyl-3-(((R)-4-methyl-5-oxo-2,5-dihydrofuran-2-yloxy)methylene)-2-oxo-3,3a,4,5,6,7,8,8b-decahydro-2H-indeno[1,2-b]furan-4-yl acetate], by 1D and 2D NMR spectroscopic, ESI- and EI-MS spectrometric, X-ray crystallographic analyses, and by comparing the ¹H NMR spectroscopic data and relative retention times (RR_t) in LC-MS and GC-MS with those of synthetic standards prepared from (+)-orobanchol and (+)-2′-epiorobanchol. The ¹H NMR spectroscopic data and RR_t of fabacyl acetate were identical with those of an isomer prepared from (+)-2′-epiorobanchol except for the opposite sign in CD spectra. This is the first natural ent-strigolactone containing an epoxide group. Fabacyl acetate was previously detected in root exudates of other Fabaceae plants including faba bean (Vicia faba L.) and alfalfa (Medicago sativa L.).     

Variation of volatiles in Tunisian populations of Teucrium polium L. (Lamiaceae)

Volatiles from wild Tunisian diploid (2n=2x=26) and tetraploid (2n=4x=52) Teucrium polium L. populations from five bioclimatic zones were assessed by GC and GC/MS. Thirty-eight compounds were identified. Main volatiles at the species level were myrcene (6; 15.3%), germacrene D (27; 9.0%), alpha-pinene (6.6%), beta-pinene (3; 5.8%), and alpha-cadinol (38; 5.1%). A significant variation among populations was observed. The tetraploid populations belonging to the sub humid and lower semi arid bioclimates showed a high amount of myrcene (6; 24.2-43.8%), those from the upper arid contain high percentages of alpha-cadinol (38; 50.6%). The dominant compounds in diploid populations, mainly located in the semi arid zone, are alpha-pinene (1) and germacrene D (27). Population chemical structure, assessed by a principal component analysis (PCA) using all identified compounds, is concordant with bioclimate and ploidy level. In situ conservation of populations should be made appropriately according to these two factors.